GeneWatch PR: New study exposes flawed claims of genome revolution

4th January 2012

A new study
published in Proceedings of the National Academy of Sciences today undermines
claims that people's genetic make-up can be used to predict and prevent the
diseases they will get (1). This claim has been central to the idea of a genetic
revolution in healthcare, in which every adult and child is assumed to have
their whole genome sequenced and stored in a database or on their mobile phone.

The study
supports earlier findings by GeneWatch UK that much of the heritability of
common diseases, calculated using twin studies, may not exist (2). Scientists
have been puzzled by the failure of large genetic studies to find genes which
explain the "missing heritability" of common diseases such as heart disease and
cancer and traits such as height. Typically, 85 to 95 per cent of the expected
heritability has not been found. Today's new study confirms that one
explanation may be that interactions between multiple genes would reduce the
predicted heritability. These interactions were not properly accounted for by
the eugenicist Ronald Fisher who developed the original twin studies method in
1918, and later analysis has not corrected Fisher's error.

"Claims of a genetic revolution in healthcare
have long been based on false assumptions" said Dr Helen Wallace, Director
of GeneWatch UK, "If heritability is much
lower than expected this means that genetic differences play only a small role
in explaining why some individuals get a disease which others do not. Genetic
testing can help people with rare disorders but will never be useful to predict
and prevent the common diseases that most people get."

Companies
which sell technologies to analyse the human genome, such as Life Technologies
and Illumina, have previously claimed that it will become routine to sequence
the DNA of every baby at birth in order to predict their risk of future
illnesses and tailor lifestyle advice and preventive medication to their
personal genetic make-up. Companies selling gene tests online to consumers,
such as 23andMe and DeCode Genetics, rely on convincing a large market of
healthy people that they should buy such tests. The idea that everyone should
have their whole genome read and stored also led to the New Labour Government's
decision to spend billions on creating a database of electronic medical records
in the NHS (3).

"Past policy decisions have been based on hubris,
lobbying by vested interests and failure to check unsubstantiated claims"
said Dr Wallace, "Sequencing the whole
genome of every person is a science fantasy that will not deliver benefits to
health".

Some genetic
studies will remain useful to identify disease mechanisms, because even small
differences in risk can provide clues about the biological pathways involved in
a disease. But the medical value of genetic testing will be likely to remain
restricted to situations where an individual is thought to be at high risk of
an inherited disease, or displaying unexplained symptoms.

The study
does not assess the usefulness of genetic screening to predict adverse drug
reactions. However, many such tests also have low predictive value and are only
useful prior to taking a few specific drugs.